This invention relates to a sliding bearing having an overlay layer, and more particularly to a sliding bearing having an improved heat emission property.
A sliding bearing, used, for example, for bearing a crankshaft or a crank pin of an engine, has an overlay layer of a uniform thickness formed on a bearing surface, made of a bearing alloy such as an Al alloy or a Cu alloy, over an entire circumference thereof. Such an overlay layer is made of a soft alloy, such as a Sn base alloy, a Pb base alloy, an Al base alloy, or a resin material. The overlay layer is formed in order to provide the bearing alloy with properties of conformability, foreign matter embeddability and anti-seizure property with respect to a mating shaft.
Lubricating oil is supplied to a sliding bearing, which serves to prevent a solid to solid contact between the bearing and the mating shaft and also has a function of transmitting heat generated during operation, that is, the function of cooling the bearing contact portion.
While the bearing contact portion is thus cooled by the lubricating oil, the sliding bearing itself is also required to have a function of heat emission to the outside. However, in the conventional sliding bearing, the above-mentioned overlay layer of a uniform thickness is formed over the entire circumference thereof, and particularly where the overlay layer is made of a resin material, heat is less liable to emit to the outside through the sliding bearing since the overlay layer has a low thermal conductivity, and therefore there has been encountered a problem that heat emission through the sliding bearing can not be effected adequately.